1. Field of the Invention
The present invention relates to a rotating device including a shaft body and a bearing unit supported in a rotatable manner with respect to each other.
2. Description of the Related Art
Rotating devices like a disk drive device are becoming compact and increasing the capacity thereof, and are built in various electronic devices. Such rotating devices are popularly built in, in particular, a hard disk drive that is a kind of disk drive devices of portable electronic devices, such as a laptop computer and a portable music player. The rotating devices like the disk drive devices built in such portable electronic devices require improved shock resistance and vibration resistance (hereinafter, referred to as “vibration resistance characteristic, etc.,”) so as to withstand against a shock due to falling and a vibration when carried in comparison with the rotating devices built in stationary electronic devices like a desktop computer. Moreover, such rotating devices require thinning and weight saving in comparison with the rotating devices built in the stationary electronic devices like a desktop computer. In general, thinning and improvement of the vibration resistance characteristic, etc., are in a trade-off relationship.
The inventor of the present invention has proposed in, for example, JP 2010-261580 A, a rotating device that is a disk drive device having a fluid dynamic bearing mechanism formed between a shaft body and a bearing unit, and having the shaft body including a shaft fixed to a base. According to the rotating device disclosed in JP 2010-261580 A, a radial dynamic bearing is formed in a space in the radial direction between the shaft body and the bearing unit, and a thrust dynamic bearing is formed therebetween in a space in the axial direction.
In the case of the rotating device that is a disk drive device disclosed in JP 2010-261580 A, in order to improve the vibration resistance characteristic, etc., it is necessary to improve the rigidity of the radial dynamic bearing (hereinafter, referred to as a “radial rigidity”). To improve the radial rigidity, there is a scheme of making a space narrower in the radial direction between the shaft body and the bearing unit both configuring a radial bearing. However, in the case of such a rotating device, if the space between the shaft body and the bearing unit is too small, the shaft body and the bearing unit contact with each other when the rotating device is rotating, disturbing the rotation thereof, and in the worst case, the shaft body and the bearing unit are highly possibly damaged.
Moreover, when the radial dynamic pressure is set to be high, the possibility of making the dynamic pressure generated at a radial dynamic bearing unbalanced becomes high. The unbalancing of the dynamic pressure may produce a negative pressure region in a lubricant. When a negative pressure region is produced in the lubricant, gases dissolved in the lubricant at that region are vaporized and bubbles are formed. Such bubbles decrease the dynamic pressure generating function when entering in the radial dynamic bearing. In the worst case, the lubricant is blasted out from a region where the lubricant is present, deteriorating the bearing function.
In view of such circumstances, the inventor of the present invention realized that in order to improve the vibration resistance characteristic, etc., of rotating devices, it is necessary to reduce the unbalancing of the dynamic pressure at radial dynamic bearing, thereby suppressing a generation of a negative pressure region.
Such a technical issue arises in the cases of not only the rotating device built in a portable electronic device but also other kinds of electronic devices.
The present invention has been made in view of such a circumstance, and it is an objective of the present invention to accomplish both thinning and improvement of the vibration resistance characteristic, etc., of a rotating device.